1. Field of the Invention
The present invention relates to optical fiber connectors, in particular ferrules in optical fiber connectors.
2. Description of Related Art
There are many advantages of transmitting light signal via optical fiber waveguides and the use thereof is diverse. Optical signal transmission requires coupling of optical fibers in an end-to-end relationship, with the coupling being one source of light loss. In an optical fiber connection, an optical fiber connector terminates the end of a cable that contains one or multiple fibers, and enables quicker connection and disconnection than splicing to another connector holding the end of another cable. The connectors mechanically couple and align the cores of fibers so that light can pass end-to-end. Better connectors lose very little light due to reflection or misalignment of the fibers. Connectors, in both parallel/multiple fiber and single fiber links, operating at multi-gigabit rates must be assembled with subcomponents fabricated with sub-micron precision (i.e., a tolerance of less than 1000 nm). As if producing parts with such precision levels were not challenging enough, for the resulting end product to be economical it must be done in a fully automated, very high-speed process.
Currently, it is generally accepted that current fiber connectors cost too much to manufacture and the reliability and loss characteristics are more to be desired. The tolerance of the fiber connectors must improve, and the cost of producing fiber connectors must decrease if fiber optics is to be the communication media of choice for short haul and very short reach applications. The relatively widespread and ever increasing utilization of optical fibers in communication systems, data processing and other signal transmission systems has created a demand for satisfactory and efficient means of inter-joining fiber terminals.
U.S. Pat. No. 7,311,449, commonly assigned to the assignee-applicant of the present invention, discloses various embodiments of ferrules that can be mass produced cost effectively by stamping. Some of those ferrules are configured for optical alignment without using alignment pins, relying solely on the alignment sleeves to provide alignment of the precisely shaped ferrules.
U.S. patent application Ser. No. 13/861,375 (published as counterpart WO 2014/011283), and U.S. patent application Ser. No. 13/440,970 (Published as US2012/0257860A1), which are commonly assigned to the assignee of the present invention, disclose improved ferrule and sleeve designs that can be incorporated in new optical fiber connectors, which results in low insertion loss and low return loss, which provides ease of use and high reliability with low environmental sensitivity, and which can be fabricated at low cost. In particular, U.S. patent application Ser. No. 13/440,970 discloses a ferrule having an open structure that has precision features formed thereon, namely open fiber clamping grooves, which can securely clamp the optical fibers without the need for epoxy or a complementary precision part. The width of the longitudinal opening defined between the lips along at least a section of the grooves is narrower than the diameter of the optical fibers to create a tight fit (e.g., an interference fit) with respect to the fibers, which allows the terminating end section of an optical fiber to be inserted laterally into the longitudinal opening of the groove, but which snuggly retains the optical fiber in the groove.
The present invention provides further improvements in ferrule designs, which provide ease of use and high reliability, and which can be fabricated at low cost.